Question

Va rog!
AM NEVOIE URGENT!!!

Answer 1

d = distanta de la un capat al drumului la celalalt

d₁ = d/3 (distanta parcursa cu viteza v1 = o treime din total)

d₂ = d - d₁ (distanta parcursa cu viteza v2 = restul de drum)

Scriem ecuatiile vitezelor si-l scoatem pe v₁:

$v_1=\frac{d_1}{t_1}=\frac{\frac{d}{3}}{t_1}=\frac{d}{3t_1}\rightarrow t_1=\frac{d}{3v_1}\\\\v_2=\frac{d_2}{t_2}=\frac{d-d_1}{t_2}=\frac{d-\frac{d}{3}}{t_2}=\frac{2d}{3t_2}\rightarrow t_2=\frac{2d}{3v_2}\\\\v_m=\frac{d}{t_1+t_2}=\frac{d}{\frac{d}{3v_1}+\frac{2d}{3v_2}}=\frac{1}{\frac{v_2+2v_1}{3v_1v_2}}=\frac{3v_1v_2}{v_2+2v_1}\\\\\\v_m(v_2+2v_1)=3v_1v_2\rightarrow 3v_1v_2-2v_1v_m=v_mv_2\rightarrow v_1(3v_2-2v_m)=v_mv_2\\\\v_1=\frac{v_mv_2}{3v _2-2v_m}$

v₁ = 25 km/h